Foreign bodies, such as bacteria and microbes pose a risk to dental health. These foreign bodies can invade canals and other hard to reach areas in dental structures and compromise dental health. It is the infections that are caused by the persistence of these foreign bodies that pose one of the greatest risks to the endodontic health of a patient.
Treatments to eliminate harmful canal contents, and therefore reduce the risk of infections, range from invasive treatments, such as extraction, to the far less invasive, yet not always effective, irrigation. Irrigation involves the use of an anti-bacterial solution to flush the canals. Today's irrigation solutions include utilizing direct lift, displacement and/or gravity pumps to move a fluid into canals, utilizing ultrasonic tips at varying rates, utilizing mechanical instruments, such as files, using positive pressure to inject fluid (for example, using a hypodermic needle) and negative pressure to remove it, and combinations of these techniques.
Studies have demonstrated that mechanical instruments alone cannot disinfect root canals. This is because large areas of canal walls, including apical, ribbon-shaped, and oval canals, cannot be cleaned mechanically because mechanical means cannot reach and come into physical contact with all surfaces within the tooth, so microorganisms in these areas can survive. Irrigation solutions are generally required to eradicate these microorganisms and various chemicals have been used for this purpose.
Ideally, an irrigant kills bacteria, dissolves necrotic tissue, lubricates the canal, removes the smear layer, and does not irritate healthy tissue. Presently, solutions that include sodium hypochlorite (NaOCl) and ethylenemide tetra-acetic acid (EDTA) are favored by dentists. The NaOCl solution, usually at a concentration between 1%-3% is used to dissolve tissue and disinfect (remove bacteria), while EDTA removes the smear layer. During an irrigation procedure, NaOCl is used initially to dissolve tissue and disinfect and EDTA is introduced at the end of the procedure to remove the smear layer. The EDTA application is followed by another flush of NaOCl or another inert solution.
Although certainly less invasive than extraction, irrigation has its shortcomings. First, NaOCl, EDTA, and other solutions found effective in irrigation are caustic solutions, including other bleaches, which when applied can badly irritate the mouth and surrounding structures. During an application, there is a risk that these solutions will perforate the apex of the canal, the end of the canal where the nerve meets the bone. If this happens, the results are so painful for a patient that the patient will end up on significant pain management, i.e., prescription pain killers, for at least two days, but sometimes, as long as two months. Second, current irrigation techniques carry a failure rate of up to 5% because often, the procedure fails to remove all the nerve tissue that is infected in the root canal system, so residual bacteria remains. Third, irrigation solutions are only effective at the time that they are applied. After a patient is treated with NaOCl and/or EDTA, the solutions are flushed out and there is no positive residual effect after the treatment is complete. Thus, any bacteria remaining in hard to reach canals will remain indefinitely and can lead to infection.
A need exists for a method and apparatus for effectively irrigating even hard to reach dental canals in a manner that produces residual benefits without causing damage and/or pain in the mouth and surrounding structures.